1. Field
The present embodiments relate to power supplies for portable electronic devices. More specifically, the present embodiments relate to techniques for managing common mode noise frequencies generated by power supplies for portable electronic devices.
2. Related Art
Flyback converters may be used to convert alternating current (AC) to direct current (DC) in low-power applications such as mobile phone chargers and/or laptop computer power supplies. For example, an external power supply (e.g., power brick) for a laptop computer may use a flyback converter to convert AC mains power from a power outlet into low-voltage DC that can be used by components in the laptop computer.
To increase the efficiency of a flyback converter, the switching frequency of the flyback converter may be varied in response to load and/or input voltage. For example, a moving load generated by a charging battery and/or the switching off of a touchscreen in a mobile phone may cause the switching frequency of the mobile phone's charger to sweep across a range of frequencies, thus lowering switching losses in the flyback converter.
On the other hand, dynamic changes to the flyback converter's switching frequency may generate common mode noise that interferes with the sensing of touch input on a portable electronic device coupled to the flyback converter. For example, the flyback converter's switching frequency may sweep through a frequency band associated with the sensing frequency of a touch control on the portable electronic device. While the switching frequency remains in the frequency band, common mode interference from the flyback converter may prevent the touch control from accurately detecting touch input on the portable electronic device. As a result, efficient operation of the flyback converter may reduce the performance of the touch control and negatively impact the user experience with the portable electronic device.
Hence, what is needed is a mechanism for managing the frequencies of common mode noise generated by power supplies of portable electronic devices.